Efficiently find and list duplicate files by size and checksum (find)
find -not -empty -type f -printf "%s\n" | sort -rn | uniq -d | xargs -I{} -n1 find -type f -size {}c -print0 | xargs -0 md5sum | sort | uniq -w32 --all-repeated=separate
Finds duplicate files faster by comparing file sizes first, then checksums, using multiple tools in combination.